1. Field of the Invention
The present invention relates to a technique for efficiently scanning an image in an image processing apparatus including an image scanning unit.
2. Description of the Related Art
Currently multifunction printers (MFPS) including scanner units and printer units are widely available as image processing apparatuses. The scanner head of a scanner unit in an MFP includes an image sensor such as a CCD and a CIS (contact image sensor). The printer unit of an MFP includes an inkjet printer or a laser printer.
An image processing circuit or the CPU of an MFP performs image processing on digital image data having been generated by scanning an image through the scanner unit of the MFP, and a printer unit prints the image using the processed digital image data. The MFP thus realizes a copy function.
An MFP generally includes memory in which three areas are allocated as an input buffer for storing digital image data, an image processing memory for image processing, and an output buffer for storing output data for printing.
Currently MFPs including inkjet printers as printer units have rapidly become widespread because MFPs are relatively small in size with low noise and can perform color copying, printing, and scanning at low cost. In recent years, MFPs have rapidly advanced in image quality and speed and thus an A4-sized image can be copied in about one minute with quality equivalent to a photograph.
However, the users and so on have demanded MFPs enabling high-speed and high-quality scanning of images. In response to the need, Japanese Patent Application Laid-Open No. 10-41256 discloses a technique enabling high-speed processing which is achieved by omitting image processing on a white area of a scanned image.
A color image processing apparatus of Japanese Patent Application Laid-Open No. 10-42156 includes white area determining means which determines a white area of an image represented by image data and image processing means for performing different image processing between on an area which has been determined as the white area by the white area determining means and on an area other than the white area. Furthermore, the image processing apparatus includes printing means for printing an image based on image data having been processed by the image processing means. The printing means performs printing while skipping the white area.
For example, the image processing means further omits a change of luminance/density and masking on an area determined as a white area.
For example, when the density level is zero as a result of density correction, the image processing means further omits scaling processing, error-diffusion processing, and masking processing on a white area.
Moreover, according to the color image processing apparatus of Japanese Patent Application Laid-Open No. 10-41256, most color image processing is performed by software. Thus it is possible to reduce the number of components, the size and cost of the apparatus, and an amount of processing of color image information to be processed.
However, according to the color image processing apparatus and method of Japanese Patent Application Laid-Open No. 10-41256, most image processing is performed, as described above, by software in order to reduce the size and cost of the apparatus.
Although the omission of image processing on a white area of a scanned image is considered, motor control for moving a scanner head so as to skip the white area at high speed is not considered. For this reason, also in a scan of an image including many white areas, the traveling speed of the scanner head results in a bottleneck, so that the speed of processing cannot be expected to dramatically increase.
For these reasons, the prior art cannot to respond to the need for even higher scanning speed.
The present invention is designed in view of such circumstances. A feature of the present invention is to provide a technique for scanning an image at higher speed.
The image includes a text image unless otherwise specified.